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OAR Informational Sheet: Pain Recognition in Laboratory Animals

OAR Informational Sheet: Pain Recognition in Laboratory Animals

Informational Sheet:The IACUC has provided a set of guidance documents (Policies, Guidelines, and Informational Sheets) for use when planning animal procedures at the University of Iowa. Informational Sheets provide information about frequently asked questions and represents guidance for best practices. Deviation from the recommendation(s) does not require specific justification.

Purpose: The purpose of this document is to help researchers and OAR husbandry staff recognize signs of pain in animals. This document does not list all signs of pain but rather lists more common and easy to identify signs of pain in animals.

All investigators should consider that procedures that cause pain or distress in human beings may cause pain or distress in other animals.1 Procedures expected to cause more than slight or momentary pain (e.g., pain in excess of a needle prick or injection) require the appropriate use of pain-relieving measures unless scientifically justified in an approved animal care and use protocol.2

Relief of Pain

Details of recommended pain relief methods and doses can be found in the IACUC Analgesia Guidelines, including non-pharmacologic (non-drug) methods which should be considered in all cases of potentially painful procedures, including those for which analgesic drugs are contraindicated by study design.

Mice

Hunched posture

Reduced grooming and ruffled fur

Reduced level of spontaneous activity

Reduced food/water intake

Separation from cage mates

Squinty-eyes

Pale eyes (if albino)

Increased aggressiveness when handled

Rats

Hunched posture

Reduced grooming and ruffled fur

Reduced level of spontaneous activity

Falling/staggering, poor gait and twitching

Reduced food and water intake

Red-staining around nose and/or eyes (i.e. porphyrin secretions)

Squinty-eyes

Pale eyes (if albino)

Back arching behavior

Horizontal stretching behavior

Abdominal pressing behavior (briefly pressing abdomen to the ground)

Increased aggressiveness when handled

Rabbit

Decreased fecal production

Reduced food and/or water intake

Reduced activity

Hunched posture

Tensing of muscles (guarding)

Bruxism (grinding of teeth)

Reduced grooming

Squint-eyed

Pale eyes (if albino)

Aggressiveness

Farm animals (i.e., pigs, sheep, etc.)

Hunched posture

Separation from flock or herd

Lack of interest in surroundings

Decreased mentation (mental activity)

Decreased appetite

Bruxism (teeth grinding)

Drooping ears

Head drooping below withers

Vocalization

Grunting (spontaneously, or when painful region palpated)

Lameness

Long durations of lying down and reluctant to stand when prompted

Restlessness

Tachycardia (rapid resting heart rate)

Dog

Hunched posture with lowered head

Decreased or absent appetite

Decreased grooming

Licking wound or surgical site

Lameness

Guarding (protecting) the painful area

Stiff gait and slow to rise

Trembling or shaking

Limited or no movement when awake

Weak tail wag or low carriage of tail

Sitting or lying in an abnormal position

Praying position (i.e. front legs and head on floor, hindquarters in the air)

Lack of normal vocalization (no greeting bark or noise)

Whining, barking or growling

Dull mentation or agitation

Inappropriate urination or defecation, or not moving away from it

Acts out of character (gentle dogs may bite or become aggressive)

Cat

Hunched posture with lowered head

Decreased or absent appetite (associated with weight loss when chronic)

Decreased grooming

Licking wound or surgical site

Bearing no or partial weight on affected limb or any degree of limp

Guarding (protecting) the painful area

Sitting or lying in an abnormal position

Trembling or shaking

Limited or no movement when awake

Stiff gait and slow to rise

Lack of normal vocalization (no noise of greeting or wanting to be fed)

Yowling or crying (with acute pain)

Hissing or growling, especially when painful area is touched

Hyperventilation or open mouth breathing

Acts out of character (aggressive or playful cats may become docile or quiet)

Inappropriate urination or defecation, or not moving away from it

Dull mentation or agitation

Ferrets

Inappetance

Lameness

Reluctance to move

Trembling

Vocalization

Teeth grinding

Hunched

Guinea Pigs

Anorexia or inappetance

Lameness

Increased vocalization

Decreased activity

Decreased water consumption

Mutilation of painful area

Hamsters

Weight loss

Excessive scratching and licking

More aggressive when handled

Vocalization when handled

Mutilation of painful area

Birds and Poultry

Vocalization

Crouched posture

Closed or partially closed eyes

Inappetence

Inactivity

Lameness

Reduced perching

Amphibians

Amphibian species such as frogs, toads, and salamanders are commonly used in laboratory animal research settings, but there is no objective means to assess the presence and severity of pain in amphibians, especially since they do not exhibit any facial expression. However, research studies have shown that amphibians are able and motivated to learn to avoid noxious stimuli.

Some exotic animal clinicians use nonspecific clinical signs such as decrease in avoidance movement (e.g., when approached by a handler) or decrease in appetite as indicators of pain in these animals.4

Fish

It is difficult to determine the nature of the response to pain in fish or whether their experience is similar to that observed in mammals. Although there have been few species-specific studies, there is evidence that fish exhibit a pronounced initial response to injuries or to contact with nociceptive stimuli or chemical algesics but their response to chronic stimuli has not been characterized.

Generally, fish react to noxious stimuli (such as puncture with a hypodermic needle) with strong muscular movements, and when exposed to a noxious environment (such as an acidic solution) show abnormal swimming behavior, attempts to jump from the water, and more rapid opercular movements. Such effects indicate some, perhaps considerable, distress, but it is not possible to describe the distress unequivocally as pain-induced.4

References

U.S. Government Principles for the Utilization and Care of Vertebrate Animals Used in Testing, Research, and Training

Pain and Distress in Laboratory Animals. ACLAM position statement approved October 29th, 2001.

Guidelines for the Assessment and Management of Pain in Rodents and Rabbits ACLAM position statement approved July 2006.